The present invention relates to computer systems (and particularly to small computer systems), and to methods for using them.
The innovations disclosed in the present application provide computer systems (especially very small portable personal computers) which have advantageous new capabilities. To better explain the significance and advantages of these innovations, the following paragraphs (down to page 7) will review some technological context. This technological context is not necessarily prior art, but is intended to help in pointing out the disclosed inventions.
Laptop and Smaller Computers
Portable personal computers were introduced in the early 1980s, and proved to be very useful and popular. As this market has developed, it has become increasingly clear that users strongly desire systems to have small volume, small weight, physical durability, and long battery-powered lifetime. Thus, small portable computers ("laptop" computers) have proven extremely popular during the late 1980s. Users continue to demand more features, longer time between recharges, and lower weight and volume. This combination of demands is difficult to meet. Moreover, as of 1990, another smaller generation of portable computers has begun to appear, referred to as "notebook" computers. This smaller form factor will only exacerbate the difficulty of the above tradeoffs.
Some Difficulties of Small Size
To meet the weight, volume, and power budgets of small portable computers, much effort has been made to re-engineer familiar components, within the limits of acceptable compromise with user comfort and convenience, to attain the needed portability. For example, almost no laptop or notebook computers have had more than two disk drives (typically one floppy drive and one hard drive); the keyboards are much smaller than would be optimal for touch typists; and the displays are much smaller than on common desktop models.
Where such compromises are needed to attain the overriding goal of portability, users readily accept them. However, if these compromises can be avoided some of the time, it is highly desirable to do so. Thus, for example, many users will "dock" their laptop or notebook computers, when on their desktops, in order to use better peripherals (faster, larger, more heavy-duty, and/or easier to use) than could be carried with the portable computer.
Portable computers are inherently more susceptible than desktop computers to accident, loss, and theft. Thus, if critical work is being done on a portable computer, backup is even more of a necessity than with a desktop computer.
The quantities of mass storage available on portables have steadily increased, but the cost per byte of the necessary ruggedized drives continues to be far above that of that of the drives normally used. This disparity seems likely to continue. Similarly, although some small portables use nonvolatile (or nonvolatized) solid-state memory to replace disk drives, the cost per byte of such memory is likely to continue to exceed that of conventional mass storage devices.
Laptops normally have a severely limited set of external ports. This limitation is imposed by several factors: first, each external connector takes up precious square inches of surface area. Second, each external connector is a point of vulnerability to electrostatic-discharge-induced component failure. Third, each external connector is a possible point of entry for dirt and moisture. Fourth, in calculating the worst-case power budget for a system, the possible power required by all connectors must be considered.
Similar problems arise from the need for bus extension. Internal space is not available for expansion cards, as in a normal personal computer; but needs for expansion still exist. Some small computers have brought out key bus lines into an external connector, but of course this is unwieldy. Other small computers have sent signals out over a port to an independently-powered extension bus controller with bus slots which would emulate the computer's internal bus.
Continuing Advantages of Stationary Personal Computers
The capabilities and cost of both stationary and portable computers have rapidly improved over the years. However, it is likely that stationary personal computers will always have some advantages over lightweight portables: it has always been true that, for a given price, stationary computers have always had more computing horsepower, larger mass storage, better displays, and better user interfaces (including keyboard, mouse, joystick and/or track ball input devices). These advantages are due to the necessary constraints (of weight, volume, power budget, and shock-resistance, and environmental resistance) which necessarily must be met by a small portable computer, and need not be met by a stationary personal computer.
Use of Both a Portable and a Stationary Computer
As small portable computers become ever more common, an increasing number of users prefer to use two computers: one for their desktop, and one more for the road. This increasingly common pattern of usage is very convenient for users, but also generates some problems.
One problem which arises is loss of file coherency: when a user edits a file on his secondary machine, he must transfer that file back to his primary machine before he again edits the same file on the primary machine.
"Docking" a Portable Computer
Users find it very convenient to "dock" a portable computer on their desktop, to a full-size keyboard and/or display. When a portable computer is used in such a configuration, users will also wish to use many of the peripherals (such as printer, modem, fax machine, tape backup devices, or additional disk drives) which are easily available with a desktop computer.
This problem becomes more urgent as useful amounts of computing power become more available in physically small portable computers.
Thus, in general, as convenient as small portable computers are, there is some difficulty getting data into and out of them. Usually the only available data routes are through a modem or through the floppy drive. (Some portable computers have LAN interface cards, but this is an expensive option, and requires a compatible LAN to interface to.) This has been recognized as a problem, and many vendors have offered external drive connections for small portable computers.
Data Interchange with a Portable Computer
Portable computer users frequently desire to exchange data with desktop computer systems. One of many ways to accomplish this data interchange is to connect the portable computer to the desktop computer by means of a cable. This cable typically connects the serial or parallel port of one computer to the corresponding port of the other computer. Data interchange is effected using complementary software programs resident on both computers.
Several problems exist in this scenario. First, the typical desktop computer has I/O ports located on the back panel of the housing. The housing is commonly sited close to a wall or cabinet, or worse, on the floor under or beside the desk. User access to the ports for the purposes of connecting a cable is cumbersome, if not impossible. Further, the required serial or parallel port on the desktop computer may already be committed to other common peripherals, such as mice, printer, etc. In this case several cables must be disconnected or connected to effect the link.
A second problem may exist in many cases. Often several cables must be connected to the portable computer to provide data communications in several formats as well as power system control, sequencing, and battery charging. Each interface or power cable is typically unique, requiring the user to perform several intricate manual activities every time the portable computer is to be interfaced.
Typically, users requiring data interchange are not comfortable with regularly re-configuring their computer system hardware. This is particularly true if such reconfiguration requires unnatural physical acts, such as crawling under a desk or leaning over a desk.
These are portable system expansion adapters in which the portable element rests upon the adapter in a horizontal configuration, such that the portable element's keyboard and display may be used in the docked configuration. Electrical interface is generally accomplished by means of a high density, high pin-count connector. Mechanically, the two elements typically interface through cams, hooks, and/or latching mechanisms. (One example of such a connection may be the Compaq LTE Docking Station, which is hereby incorporated by reference.) Advantages of such arrangements include: High data-rate interconnect; No user requirement to manipulate cables; Portable computer's keyboard and display usable while interfaced. Some disadvantages include: Connector/Mechanism Cost; Potentially low reliability of high-density connector; Interface alignment is critical, requiring potentially intricate user manipulations.
Innovative Computer System and Method
The present invention provides a new way to reconcile the demands and capabilities of stationary and portable personal computers. The present invention teaches a macro-system which includes at least one portable computer and at least one stationary computer, and the stationary computer system includes a docking bay in which the portable computer is physically inserted whenever the user has returned with it to his primary work area. This docking station includes contact probes which automatically make contact to a small number of contacts on the back of the portable computer whenever it is stuffed into the docking station. The portable computer preferably includes soft power switch logic, so that an activation signal, received when the portable computer is docked, can be used to wake up the portable computer and bring it up active in a slave operating mode.
The combination of spring-loaded axially-moving pins, in the docking bay, with flat contact pads on the portable unit provides a very robust structure. This structure provides great ease of use, and good reliability.
Appropriate software routines can then be triggered to maintain file coherency. For example, a TSR program or background process on the stationary computer can be used to sense whenever the portable computer has been docked, and launch a file comparison process. This process can compare all files with common path and file names, on the portable and stationary computers, to see if any of them have more recent dates shown on the portable computer. (This process can also compare the real-time clock values, of the stationary and portable computers to correct for any offset in real-time clock values.) Alternatively, of course, this file comparison and update procedure can be modified in a variety of ways familiar to designers and users of file management utilities. For example, to limit the scope of comparisons (and therefore the time required for automatic update), categories of files to be compared can be included or excluded by path name or by suffix or otherwise. For another example, the process can include a query which ascertains which portable computer has just been docked, and the process can maintain a small data file of its own listing time of last update for each possible portable computer, and the process can then simply look for files on the portable computer which have dates since the last update. Similarly, the updating in the opposite direction (from the main stationary computer to the portable computer) can be amassed by data file selection list, and also can be manually triggered, when the user is about to undock or can be automatically performed as a background process whenever the stationary computer is idle after a file save has occurred.
For durability and environmental resistance, it is inherently desirable for portable computers to fold up into some reasonably compact shape which conceals vulnerable portions as much as possible. Thus, notebook computers normally fold up, in a clam shell configuration, so that the display and keyboard are on the inside of the clam shell, and protected, when the notebook computer is closed. The present invention takes advantage of this characteristic by docking the portable computer in its closed configuration into the docking bay on the stationary computer.
No multi-pin connectors, such as are commonly used for cabling a data link, are used in the presently preferred embodiment. Instead, spring-loaded probe pins, in the stationary docking bay, are used to contact exposed flat contacts on the back side of the portable computer. More precisely, these exposed flat contacts are on whichever side of the portable computer is to be inserted first into the docking bay. If the portable computer has a handle, this would be the side opposite the handle.
Note that the present invention is not necessarily limited to "notebook" portable computers. It can also be applied to "laptop" size portable computers, or to "palmtop" or smaller portable computers. In particular, the disclosed system is not necessarily limited to portable computers which rely primarily on keyboard input. The disclosed system can also be used with portable computers which use both keyboard and stylus input, or to portable computers which use stylus input alone, or to portable computers using other input configurations as such are developed.
In the presently preferred embodiment, the docking bay is a rectangular parallelepiped, which includes internal ribs to guide portable computer into its docking position with minimal friction. However, other parallelepiped shapes can readily be substituted. In a further alternative, the docking bay may have a wedge or pyramidal shape, if the back portion of the parallel computer has a tapered wedge shape.
In any case, note that the interior of the docking bay must fit the 3-dimensional physical shape of the exterior of the portable computer.
Of course, different models of portable computers may have same external shape, and thus be usable with the same docking bay.
Note also that (provided a portable computer has the accessible docking contacts in the defined shape, with the defined electrical relations), the only element which may have to be customized to a particular portable computer model is the shape of the docking bay. However, this is simply a piece of molded plastic. Therefore, sellers of portable computers which include the contacts for such a "smart dock" can supply an appropriately customized docking bay shell, if needed, to ensure that their portable computer models will be compatible.
Some noteworthy advantages of the present invention include: docking requires only a low insertion force; No Latches, Cams, or levers need be operated for docking; the interconnect is a High-reliability Low-density interconnect; the Pin (male) elements are protected by sleeve; the Pad (female) elements on the portable unit extremely are extremely rugged; cost is low; and the system is very convenient for the user.
ESD Protection
The contacts at the back of the portable computer, in the presently preferred embodiment, are more exposed to electrostatic discharge (ESD) than are the conductors in conventional stereo, parallel, keyboard, and video connectors which may be found on the back of a normal portable computer. Thus, in the presently preferred embodiment, additional protection is provided against damaging internal electronic components by ESD.
Serial port interface chips are preferably used, inside the portable computer, for interface to these contact pads. Serial port interfaces normally include significant ESD protection. However, if additional protection is required, other known expedients can be used, such as shunt-connected Zener diodes, series-connected resistors, and/or fast-blow series fusing.
In addition, some mechanical protection against accidental fingertip contact can be provided simply by placing low ribs around and between the back contact pads.
In a further alternative embodiment, a trap door arrangement can be used to selectively expose the back contacts only when the portable has been inserted into its docking bay. However, the additional mechanical complexity this entails is highly undesirable.
In the presently preferred embodiment, the docking bay includes feet which support it in an upright position. Thus, the portable computer can be inserted into its docking bay like a book into a bookcase. However, in a contemplated alternative embodiment, the docking bay can be set to open upwards, so that the portable computer is simply lowered into the docking bay. Thus, gravity helps to maintain a good contact between the contact heads on the back of the portable computer and the probe pins inside the docking bay.
In the presently preferred embodiment, the portable computer can be inserted into the docking bay in either of two orientations. This can be accomplished in two ways. The preferred way is to include two sets of probe pins, in complementary locations inside the docking bay, so that the contact pads on the back of the portable computer will meet a set of probe pins in either orientation. Alternatively, it would be possible to define the location of the contact heads on the back of the portable computer to be symmetric, with additional logic for ascertaining which orientation is present and for rerouting signals accordingly. This is not preferred, because it places additional constraints on the designers of portable computers.
Note that if two sets of probe pins are used in the docking bay, the area of the contact pads on the back of the portable computer must fall over the axial center of the back of the portable computer, to keep the two sets of probe pins separate. Note that also this double orientation capability is an optional feature, which can be included in the docking bays for some models of portable computer and not included in the docking bays for other models of portable computers.
Note also that the location of the contact pads, on the portable computer, is not necessarily on the back of the system chassis. For instance, on a notebook computer with dimensions on the order of 7.times.10.times.2 inches, the keyboard will normally be oriented so that its width is limited only by the largest available dimension of the system chassis. Thus, the smallest of the six sides of the notebook computer will be the two end sides to the left or right of the keyboard. One of these sides will typically be taken up by a floppy disk drive, but otherwise these sides are likely to be less intensely populated than the back of the portable computer. Thus, for some models of portable computers, these sides may be the most advantageous location of the contact pads.
In the simplest embodiment, data interfaced through the contact pins is built around a serial data interface. Thus, signals routed to the back contact pads will include the three serial lines (Rx data, Tx data, ground), and preferably one pin for presence detect as well as a pair of pins for handshaking signals (such as CTS/RTS).
Note that the mechanical arrangement prevents sideways forces from being applied to the probe pins.
Preferably, the signals from the probe pins are brought into the host computer through a serial port connector. A small amount of glue logic is preferably used for presence detect; for example, a microcontroller in the portable unit can implement both presence detect and power sequencing.
Alternatively, of course, in a motherboard which is designed from scratch to accommodate this capability, a dedicated connector can be brought out to the edge of the mother board.
Note that the axially-contacted pins used in the presently preferred embodiment are not well suited for very high current density. Thus, for applications which require higher current density (e.g. for rapid recharging of batteries in a portable item), a conventional wiping contact arrangement may be better. However, if needed for such applications, the capability to manually connect a high-current contact for battery recharge can be added to the simple drop-in signal contact arrangement of the presently preferred embodiment. Alternatively, where a small amount of charging current will suffice, it can be provided by multiple axially-contacted pins connected in parallel.